You're at a movie theatre and the kids behind you won't stop babbling. Not a problem. You reach into your bag, whip out your trusty speech-jamming gun, whirl around in your seat and blast them. No more nattering.

This isn't a theoretical scenario; this silencing device actually exists. The team of Japanese researchers that created it call it "SpeechJammer," and it could soon be coming to a theatre (or library, or conference hall) near you.

SpeechJammer works by exploiting a mind hack that psychologists have known about for ages: most people find it incredibly difficult to continue talking when the words that they're speaking are replayed to them on a slight delay.

With this in mind, researchers Kautaka Kurihara and Koji Tsukada created the handheld speech-jamming device. The first SpeechJammer was simple. It consisted of a directional microphone and a directional speaker that allowed you capture a person's voice and play it back to them with a delay of around two-tenths of a second. In later prototypes, like the one pictured here, the researchers incorporated a distance sensor and a laser pointer to make it even easier to target people individually.

There's also the question of whether this device could one day be used as a weapon against free speech. In an interview with Technology Review, Kurihara and Tsukada said that the SpeechJammer could be used to "facilitate discussion" in group meetings, and that "we have to establish and obey rules for proper turn-taking when speaking"; which, in the right (or wrong) context, sounds weirdly dystopic and totalitarian.

Still, a device that could help put an end to chatty moviegoers? That's awfully damn tempting.